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In this letter, image receivers are characterized to address the challenges of indoor positioning with optical wireless location systems. Image receivers are studied according to their field-of-view (FOV) characteristics: 1) the first image receiver uses a wide-FOV (95°) microlens and 2) the second image receiver uses an ultrawide-FOV (130°) microlens. An angle of arrival characterization of the image receiver is used to quantify azimuthal, φ, and polar, θ, angles of incident light from optical beacons. A dilution of position (DOP) characterization is used to quantify geometrical effects of the optical beacon distribution. It is found that the ultrawide-FOV microlens (with a mean positioning error of 1.5 cm) can better image widely separated optical beacons, and thus operate at a lower DOP, compared with the wide-FOV microlens (with a mean positioning error of 3.2 cm). Index Terms-Angle of arrival (AOA), indoor optical positioning, image sensor. 1041-1135

The challenges of optical wireless positioning are addressed in this work, by a thorough investigation of angle of arrival (AOA) positioning characteristics. The overall positioning precision for AOA positioning is studied in terms of two contributing factors-being angular precision and geometric dilution of precision (DOP). Angular precision is characterized for an optical wireless receiver having an especially wide angular field-of-view (FOV). Geometric DOP is characterized for optical beacons deployed in the form of triangle, square, and hexagon cell geometries. The mean and standard deviation of the positioning errors are extracted from the positioning error distributions for each of the three cell geometries. It is found that the overarching goal to establish low and uniform positioning error distributions can be met by implementing an optical wireless receiver with a wide angular FOV and by implementing the optical beacon geometry with a correspondingly small height-to-side-length ratio. The prospects of these findings are discussed for future optical wireless positioning systems. Index Terms-Angle of arrival, dilution of precision, optical wireless positioning. I. INTRODUCTION PTICAL wireless networks are increasingly attractive implementations for indoor networks. Optical wireless communication (OWC) systems have been shown to support high data rates [1,2], with performance levels that can surpass those of traditional radio-frequency Wi-Fi communication networks [3]. Likewise, Optical wireless location (OWL) systems have been shown to support accurate indoor positioning [4], with performance levels that can surpass those of radio-frequency Wi-Fi positioning networks [3]. OWL systems, in particular, are now emerging as tandem positioningcommunication systems or as dedicated positioning systems [5], through rivaling implementations. The standard OWL implementation is based upon received signal strength (RSS) positioning [6]. An RSS positioning system employs overhead optical beacons, typically comprised of light emitting diode (LED) transmitters, along with a mobile optical wireless receiver, typically consisting of a single photodetector. The optical wireless receiver detects incident optical powers from the distributed optical beacons, and uses a prescribed algorithm to weight these incident optical powers

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